The thermal protection offered by currently available protective garments which employ thermally insulating textiles to trap layers of air may be altered by varying the amount of trapped air. This may be achieved by having the wearer add or remove garment layers. However this requires the wearer either to carry a number of garments or to wear a garment adapted to protect against the largest likely change in ambient temperature. As thermally protective garments tend to be bulky both solutions are likely to prove cumbersome to the wearer. Additionally, the wearing of a garment which provides protection against the largest potential change in ambient temperature, for example in situations where there may be a likelihood of fire or a risk of exposure to cold, may place thermal stress on the wearer in the absence of these situations.
As an alternative to increasing the number of garment layers in order to achieve an increased thermal protection the air gap between two layers of a garment may be increased. Thus, by providing a garment in which the air gap may be varied variable thermal protection may be achieved. One known fabric which may be utilised to provide such a variable air gap garment is described in GB 2 234 705 A and comprises a material having two parallel material layers between which is disposed fibres, the height of which may be manually varied by the effecting a relative movement of the layers. This solution requires the wearer to pull on one or other of the layers by, for example, zipping and unzipping gussets in order to vary the thermal insulation and has the disadvantages that the wearer must stop what he or she is doing in order to adjust the garment and in that the wearer may not respond quickly enough to rapid environmental changes to provide timely thermal protection.